Field of the Invention
This invention relates to a device for rapidly feeding sheet inserts to a pusher conveyor of a packaging machine.
In machines for packaging flat products of a graphic or editorial type, such as sheets, signatures, magazines, brochures etc., these products, known hereinafter for convenience as "sheet inserts", have to be fed, for example, individually onto a conveyor. The conveyor conveys them to a unit for their packaging within a plastics film or a suitable paper sheet. Such inserts mostly require to be fed in a certain additional number to a base product, a high operating rate being essential.
Up to the present time so-called drum feeders have been used positioned to the side of the pusher conveyor of the collection line, to feed the individual inserts onto the editorial base product. By using a certain number of drum feeders for single inserts or sheet elements positioned one after another, the required product containing a number of such inserts is gradually formed. Such an arrangement has certain technical drawbacks.
In this respect, the fact of laterally positioning drum feeders or other types of feeders means that the single insert or similar fed product reaches the collection conveyor in a perpendicular direction at 90.degree. to the direction of movement of the pushers which advance with the conveyor. In such a case there is a sudden directional change of the fed product, resulting in a reduction in production rate proportional to the type of product collected by the conveyor. This reduction is due both to problems of possible product damage and to problems of correct feed to each individual pusher, because, for example, the product has to be added to and superposed on another which has already been moved forward by the advancing pushers.
If the inserts are light in weight or are of little rigidity, this problem becomes even more serious because of the danger of damage and the poor stability of the insert if fed to the conveyor at high speed.
In general, feeding the various inserts at 90.degree., whether they are to be added to others or not, requires a pitch between one pusher and the next which is sufficiently large to prevent interference arising on lateral insertion which would prevent the sheet inserts assuming their correct position. This also influences the maximum advancement speed, resulting in a potential production loss and an increase in production costs.